Office



I UNITE STATES FFICE.

PATENT I THOMASO. ROCHE, OF BROOKLYN, ASSIGNOR THE E. & H. T. ANTHONY &

COMPANY, OF NEW: YORK, N. Y.

PHOTOGRAPHKIC PLATE.

SPECIFICATION forming part of Letters Patent No. 519,646, dated May 8, 1894.

Original application filed January 31, 1893, Serial No. 460,470. Divided and this application filed April 20, 1893. s ial N 471,213- (No specimens.)

' To aZZ whom it may concern:

Be it known that I, THOMAS C. ROCHE, a citizen of the United States, and a resident of the city of Brooklyn, in the county of Kings and State of New York,have invented anew and useful Photographic Plate or Film, of which the following is a specification.

My invention relates to improvements in photographic plates or sensitive surfaces, and

the purpose of the invention is to prevent halation of the sensitive surface.

Before explaining the invention, it will be well to define somewhat the state of the art as at present. practiced. It is as follows: To

I 5 prevent halation to some extent at least, the old silver plates and collodio emulsion plates have heretofore been coated on the back with an-opaque non-actinic color, usually mixed with gum, or have had dark paper pasted on the back. This was done to prevent the re fiection from the back or rear side of the transparent support. Also the modern gelatine dry plates, now mostly used, to which-my invention applies, and which are from twenty to fifty times as rapid as the old collodion plates, show halation badly, and the old mode of backing is used on them, which has to be cleaned off, before development. Lately a new mode of preparing gelatine plates to avoid halation has been introduced, '5. e., the plates are first coated with a medium slow emulsion; when this is dry, they are coated again with another emulsion, about twice as sensitive, and then a third time coated with 5 an extremely quick emulsion. This mode of preparing the plates is slow and expensive, requiring from ten to twelve hours drying between each coating. Most interiors require long exposures, and where the light is strong 0 in front of the lens, as stated above, there is produced on this extremely sensitive surface, '5. e., the outermost one, a reverse picture, that is to say, a positive in place of a negative on development. On this account plates so made 5 are not so desirable for most kinds of work.

' What I have invented and discovered is, that plates can be coated on one side only with a single sensitive coating of gelatino bromide of silver or gelatino bromo iodide of silver emulsion, which will accomplish the desired effect of stopping halation for all practical purposes. Instead of coating the back of the glass or other support for the sensitive'surface with an opaque backing,l prevent the rays of light, measurably at least from entering the support for the sensitive surface, by applying coloring materialmixed with the sensitive emulsion, on the front side of the glass or other support. The coloring matter which I employ is non-actinic, and is soluble in water or weak acids, so that it may be readily washed out.- The coloring matter must also not be injurious to the sensitive coating. By that I mean that the coloring material must be of such a character that it will be inert in action in the emulsion and also in the chemical processes to which the plate is subjected during development, fixing and washing, and inasmuch as vegetable coloring matter is liable to quick decomposition,

especially when brought in conjunction with moisture, I do not use them, on the contrary I use non-actinic mineral colors only, preferably thoseof the analine group, andI prefer to use green, yellow, orange and red.

There are various methods of applying the coloring matter, as above stated. I confine this present application which is a division of my application Serial No. 460,470, filed January 31, 1893, to one method only, as fol- 8o lows:

I mix the coloring matter with the sensitive solution prior to applying the same to the transparent support. To do this, I add a sufficient portion of the coloringmatter directly 8 5 to the fresh sensitive emulsion just previous to coating the naked plates or film supports 7 with it. Then the plates or supports are coated in the usual manner. A formula for this method may be: distilled water, five 0 ounces, coloring matter about twenty grains; one and one-half to two ounces of this solution to one quart of the sensitive emulsion. The denser the coloring the longer the exposure may be without detriment to the results; and in stating the above formula, I

have used the coloring matter known as uranine as a basis. When using other coloring matters, a deviation from the above proportions may be found desirable.

By my method of mixing the coloring matter with the sensitive emulsion, I secure peculiarly uniform films; the coloring matter being present in equal proportions throughout the entire film, and not more at one point,

t. e., on the surface, than at other points, which for certain uses is objectionable.

The character of the base upon which the sensitive layer is supported is immaterial, provided it be transparent. It may be glass, collodion films, celluloid, paper, suitably prepared mica, and the like.

After the film or plate has been exposed, developed, and fixed, it requires a thorough washing. If, after this washing, there remains any 0E color in the plate it should be immersed in a solution of water twenty ounces, muriatic acid one dram,the dish containing the solution and plate being rocked for a short time. A strong solution of alcohol may be used for the purpose. Then wash well for final cleaning.

I wish it to be understood that I do not limit myself to uranine alone, as any color sufficiently non-actinic, and which is not injurious to the silver and which is soluble in water, alcohol,alkali, or weak acid will answer the purpose.

I claim- 1. A transparent support, such as glass, collodion films, mica, celluloid, paper, 850., coated with a homogeneous, uniformly colored film in substantially the proportions set forth, of sensitized gelatiue emulsion and non actinic inert coloring matter of mineral ori gin, which is soluble in water, weak acid, alcohol or alkali, substantially as and for the purpose set forth.

2. A transparent support for a sensitive coating, having upon one surface, a homogeneous, uniformly colored layer, composed in substantially the proportion set forth, of sensitive gelatino argentic material and nonactinic inert soluble coloring material of mineral origin, substantially as and for the purpose set forth.

Signed at New York, in the county of New York and State of New York, this 14th day of April, A. D. 1893.

THOS. O. ROCHE.

Witnesses:

PHILLIPS ABBOTT, JOHN E. LACEY. 

